The present invention relates to a method and apparatus for traffic-dependent controlling of means for controlling traffic.
Traffic-dependent traffic controlling takes place today for example via traffic signal installations, alternating traffic signs, changeable parking space information signs or radio announcements. The traffic-dependent data is obtained via traffic detectors such as induction loops, radar detectors, or infrared detectors.
For example, given traffic signal installations as means for controlling traffic, the phase sequences or signal sequences thereof are determined by predetermined signal programs. The signal programs can thereby be varied according to the selected control method. Thus, in traffic-dependent control methods, e.g. the time duration of the individual phases, the sequence of the individual phases and the number of different phases (given need-related requests) in the signal program are changed. In time-of-day-dependent control methods, different signal programs, and thus different phase sequences, are switched at fixedly predetermined times of day (e.g. in peak traffic hours).
For the selection of the signal program or, respectively, for the selection of the phase duration, the sequence of phases or the number of phases, traffic-related characteristic quantities are evaluated that are determined using the traffic detectors. In the case of a signal program with fixed times, the characteristic quantities are converted off-line during the design processing. In the case of a signal program adaptation or signal program formation, the characteristic quantities are processed continuously, with the possibility of a controlling alternating between traffic flow and signal controlling. The momentary signal programs are thereby calculated on-line and evaluated according to a predetermined control logic, on the basis of respectively updated characteristic quantities. With the aid of traffic detectors, occupation values are detected in the spatial surroundings of the traffic signal installations, from which values characteristic quantities of the traffic flow are derived. Characteristic quantities include for example the wait time of the vehicles at the traffic signal installation, the length of the traffic queue at the traffic signal installation, the traffic heaviness, i.e. vehicles per cross-section, travel speed, signaling (request) by pedestrians, cyclists and/or vehicles, degree of occupation, traffic density, degree of capacity utilization and the load quotient. Given a traffic-dependent signal program selection, the prepared characteristic quantities of the traffic flow are combined in the control logic for the selection of the signal programs with conditional equations and threshold values.
From the reference "Richtlinien fur Lichtsignalanlagen" ((RiLSA)--Lichtzeichenanlagen fur den Stra.beta.enverkehr--ed. 1992, published by the Forschungsgesellschaft fur Stra.beta.en- und Verkehrswesen, Arbeitsgruppe Verkehrsfuhrung und Verkehrssicherheit, pp. 46 to 47, as well as Appendix D, pp. 90 to 110), it is known how control logics are represented using flow diagrams. The phases and phase sequences of the traffic signal installation that are useful for the traffic-dependent controlling are thereby shown in a phase sequence plan. The exchange between the phases is defined precisely and is shown in comprehensible fashion in the phase transition. A flow diagram contains the logical and chronological conditions for the duration of the phases and for the switching of the phase transitions, and thus completely represents the sequence of the traffic-dependent controlling. Logical conditions thereby hold for the combination of the characteristic quantities of the traffic flow, and chronological conditions predetermine the chronological context of the program sequences, such as for example minimal and maximal clearance times of a signal group given free circulation time. Only a single flow diagram is thereby to be represented for all signal programs. This single flow diagram becomes increasingly difficult to understand as the complexity of the control logic increases, and a translation of the conditions prescribed in the flow diagram into a traffic-oriented description that a control apparatus of a traffic signal installation can interpret becomes increasingly difficult.